1. Field of the Invention
The present invention relates to an image forming method used to develop an electrostatic latent image in an electrophotographic method and electrostatic recording method.
2. Description of the Related Art
In an electrophotographic method, an electrostatic latent image formed on the surface of a photoreceptor (latent image holding member) is developed as a toner image by using a toner containing a colorant, the resulting toner image is transferred to the surface of an image recording member directly or through an intermediate transfer member and the transferred toner image is fixed using a heat roll or the like to obtain an image. In the meantime, the latent image holding member is usually cleaned to use it again for the formation of an electrostatic latent image. A dry developer to be used in such an electrophotographic method and the like is roughly classified into a one-component developer which singly uses a toner prepared by compounding a colorant and the like in a binder resin and a two-component developer obtained by mixing a carrier in the toner.
In a general electrophotographic device using such an electrophotographic method, the electrostatic latent image of the latent image holding member is developed using a toner, the toner image is transferred to a receiving member such as an intermediate transfer member and then, the toner image finally transferred to an image-receiving member is fixed in a fixing device. In this case, a toner left untransferred on the latent image holding member after toner transfer is collected in a recovery container by cleaning using a cleaning device and then dumped. Therefore, if this remaining toner can be reused as recycled toner, valid utilization of resources can be achieved.
However, it is pointed out that if the remaining toner is used as recycled toner, problems concerning background pollution, scattering of toners and the like are easily caused because a paper powder of transfer paper (image-receiving member) is intermingled in the toner and toners in which external additives are embedded and finally peeled off are intermingled.
There is a method proposed as techniques for effectively utilizing remaining toner as recycled toner in Japanese Patent Application Laid-Open (JP-A) No. 7-209902 wherein each ratio of the amounts of a releasing agent and external additives between recycled toner and initial toner is defined to limit the deterioration of a carrier thereby improving durability. There is also a method proposed in JP-A No. 11-95553 to better the fluidity and charge stability of a developer by such a combination of an initial toner and a refill toner as to keep the condition that the amount of the external additive in the initial toner is less than that in the refill toner. Further, there is a method disclosed in JP-A No. 11-153881 which method can raise transfer efficiency and decrease a waste toner in a toner composition comprising toners to which two types of fine particles different in sphericity and charge are added and a mother toner to which any fine particle is added by using such a combination that the charge of the mother toner falls between the charge quantities of the toners to which two types of fine particles are added.
However, all the above methods are insufficient as measures for obtaining a high quality image stably by using recycled toner.
In the meantime, in order to maintain the characteristics of a photoreceptor as a latent image holding member for a long term, it is required to control the photoreceptor as a system such that the surface of the photoreceptor is worn to some extent. When the wear of the photoreceptor is too small, the surface of the photoreceptor is polluted, and some defects are tend to occur. The defects include a “white spot” phenomenon, in which image density decreases in copies and print images, and an “image running” phenomenon, in which character images are blurred. Moreover, it is necessary to make the wear to occur uniformly over the entire surface of the photoreceptor.
Therefore, in the case of using recycled toner, it is necessary to keep the photoreceptor uniformly worn.
As a cleaning method for removing remaining toners on the surface of a photoreceptor, there are various methods such as methods using a fur brush or magnetic brush and methods using a cleaning blade formed of elastic material. A method in which a cleaning blade formed of elastic material is used to rub the surface of a latent image holding member, thereby scraping a toner off (this method is sometimes referred to as “blade cleaning” hereinafter) is inexpensive and exhibits stable performance and is therefore usually used. However, this blade cleaning may cause various defects such as wear and scratches of the latent image holding member and it is therefore necessary to control the blade cleaning precisely so as to avoid such defects.
In order to control the blade cleaning stably, a method is proposed in which a titanium oxide particle which has been treated with a fatty acid metal salt, a titanium oxide fine particle which has been surface-treated with hydrolyzing a fatty acid compound in an aqueous system, an inorganic compound which has been surface-treated with a fatty acid metal salt, a fine particle titanium oxide which has been made hydrophobic by surface treatment using fatty acid aluminum or the like is added to a toner particle (see, for example, JP-A Nos. 4-452, 5-66607, 5-165250 and 10-161342). In these methods, the aforementioned problem originated from the size of the particle diameter of the fatty acid metal salt itself is avoided to some extent by using the fatty acid metal salt for surface treatment. However, damages to the surface of a photoreceptor is prevented insufficiently though all these methods have a certain effect.
Meanwhile, in, for example, JP-A No. 2-89064, a hydrophobic hard fine powder is externally added to a toner to abrade a photoreceptor by the abrasive effect of the hard fine powder, thereby preventing toner filming. However, though this method is effective to restrict filming, it has the drawback that the surface of a photoreceptor is worn, which significantly shortens the life of the photoreceptor. Also, a cleaning blade is worn by the hard fine powder and the life of a blade is significantly shortened.